The present invention relates to a throttle actuator for controlling the amount of gas suctioned into an engine and, more particularly, to an electronically controlled throttle actuator in which control operation is made more precise and flexible so as to favorably ensure safe driving even when a failure occurs in the control mechanism or in a control device.
In a conventional electronically controlled throttle actuator, opening of a throttle valve is adjusted by operation of an accelerator pedal transmitted by means of an accelerator cable, which operation is supplemented by operation of an electronically controlled motor, as disclosed, e.g. in Japanese Patent Laid-Open No. 62-186022.
In the throttle actuator disclosed in Japanese Patent Laid-Open No. 62-186022, the throttle operation is performed mainly with the accelerator pedal. Normally, the motor is kept at a position such that no torque is transmitted from the motor to a throttle shaft. When needed, the motor is rotated to a position such that torque is transmitted to the throttle shaft, and then the motor controls the opening of the throttle valve. Thus, there are unsatisfactory features: response delay is likely during the initiation of the throttle control; a minute angle adjustment of the opening is not easy to perform; and at initiation of torque conduction from the motor to the throttle shaft, an impact caused by the inertia force of the motor transmits to the driver through the accelerator pedal.